I can't really tell from the images you posted, but it sounds to me like one of your toner cartridge locks are not completely rotated into the down and locked position. Have you changed a toner cart recently? If so, suspect that one first.
When diagnosing print quality issues, pictures speak a thousand words.
If you can, please scan or take some pictures of the 20% density pages for EACH color and post them with your reply.
The problem appears to be with your red toner cartridge. I suggest you pull out the red toner cartridge and then push it back in before trying to print again. If this doesn't fix it then replace the red toner cartridge.
Troubleshooting this problem is aided by understanding the basic process of how a laser printer works. ie Static electricity attracts toner on to roller which then rolls it on to the paper. The toner is then fused on to the paper by high heat.
In this case I can see that toner is not being applied to the paper along one side of the page. If it was then it would smudge. ie the problem must be with either static not being applied to the roller or there being a fault with the toner cartridge, or the way the toner cartridge is installed.
I would agree with "mbarraus" that one of your toner carts is not seated corrected, but not the cart he indicated.
OK..... the details of why...... (you have to know how this machine is built to really understand this)
The reason this happened is because as the carousel (the big thing in the center of the printer that holds the toner carts) rotates, each time it stops to transfer a color, the toner cart of the "next color" in sequence is very close to the laser beam path, in this case Cyan. If the locking handle on that cart is protruding at all, it will block the laser beam and the result will be a huge blank area down the side of the page.
This is going to sound weird, but use the front panel to replace the Cyan toner, remove and re-seat the Cyan toner cartridge. Ensure the rotating toner lock handle is completely rotated all the down into the locked position. This is very important. As you view the carousel from the front where you replace the carts, rotation of the carousel is downward.
Yellow lock can effect Black
Magenta lock effects Yellow
Cyan lock effects Magenta
Black lock effects Cyan
Also, please verify.... Is this the bottom of the page, or the right side of the page? If this is the bottom, we're looking at a completely different cause and everything suggested above is invalid.
Fixed! I wish I had asked you for assistance when this problem first occurred - it would have saved me hours of frustration AND $170 for a drum I didn't need.
Llynster - the 20% density tests showed that it was the magenta cartridge that was not laying down color properly (as suggested by mbarraus) along the side of the page (not at the bottom). I've posted magenta test below, but the other test results (except for the black) were so faint neither my scanner or my camera could adequately capture them; however they all printed evenly.
Based on your follow up message, I removed and replaced the cyan cartridge (apparently more firmly than I had done any of the numerous other times I had done this with all the cartridges) and the magenta cartridge now prints properly.
This leads me to another question about setting the printer to allow Photoshop to control the colors, however, I will post that in a separate thread so that this one can be marked resolved.
Thank you very much for your help - and please look for my next post.
Glad to help. Happy printing !!
I'll take a stab at your new post when I see it.